The Nitrifyinrj Ferments of the Soil. 703 
'and equally good in all other respects, but the one containing 
within reach of the roots during a season's growth twice as 
much available nitrate as the other. If the latter will only 
grow in a good season fifteen bushels of wheat per acre, the 
former will yield thirty; should it contain half as much again 
I of available nitrate, it might even yield close on forty-five bushels. 
'Yet the quantity of this most important factor of a soil's fertility 
present at any one time is, in relation to the mass of soil, 
almost infinitesimal. Place a handful of soil in the hands of a 
chemical student, and, unless he employs the most refined and 
I delicate chemical tests, and adapts his plan of analysis specially 
to detect this ingredient, he may miss it altogether. Indeed, 
' in some soils, and under some circumstances, as, for example, in 
i the soil of a field of grass in vigorous growth during a showery 
June, or in a worked-out, sandy soil, after an autumn of per- 
■ sistent rains, the most sensitive chemical test will barely detect 
it. Sometimes there is less than one part, often less than ten 
parts, in a million parts by weight of soil ; sometimes there is 
ten times as much as the larger of these quantities. 
Small as are these proportions, the modern refinements of soil- 
sampling and of analysis permit an accurate estimate to be made 
in any given case, and to fix the ideas we may glean a few of 
the results obtained in the Rothamsted laboratory on the soil of 
the celebrated Broadbalk wheat field. Sampled in October, and 
therefore containing the nitrate (if any) unconsumed by the 
summer's wheat crop, and that accumulated since its removal, 
' the plot that had grown a crop of wheat yearly for forty years 
I without manure showed' 15 lb. of nitrogen as nitrate per acre 
to a depth of twenty-seven inches ; the plot growing wheat 
every year with 14 tons farmyard manure per acre showed^ 
52-2 lb. of nitrogen as nitrate per acre to the same depth. The 
soil of another field in fair condition, bare fallowed since the 
harvest of the previous year, showed 60 lb. of nitrogen as nitrate 
per acre to the same depth. 
This mode of statement is no doubt the most convenient 
from an agricultural point of view. It emphasizes the well- 
ascertained fact that the commanding influence of nitrate of 
lime on plant growth is a consequence of its supplying the 
plant with nitrogen in an immediately available foiTn wherewith 
to build lip the albuminoids of the protoplasmic contents of the 
living cells which are the plant's manufacturing organs, and 
' Equal to 881b. nitrate of lime, or 1081b. nitrate of potash, or about 12 
parts of the latter per million of soil. 
Equal to 3061b. nitrate of lime, or .3761b. nitrate of potash, or about 42 
parts of the latter per million of soil. 
